hg-http: made port configurable
since the ports for the
are already configurable, this completes what's needed to run
HDK installations side by side.
For the record, Gunicorn is happy serving Unix Domain sockets, but Heptapod Workhorse cannot use them yet (heptapod-workhorse#4 (moved))
(MR done on top of !1 (merged), which will be published soon anyway)